The Research On Dynamic Characteristics Of Surrounding Rock Of Grottoes Reinforced By Pre-stressed Cable Under Earthquake

These grottoes, which have been built long years ago, however, have been subjecting to the weathering and erosion due to wind, rain, sand and sunlight and sometimes suffered from the damage caused by earthquakes and human activities. As a result, these grottoes are rather vulnerable under earthquakes. Since the seismicity in China are generally rising and many of these grottoes located in high seismicity zone, it is very important to carry out study on the characteristics of dynamic damage of surrounding rocks of the grottoes to provide measures to improve seismic resistance of these grottoes.In this dissertation, three contents are refered:(1) In this paper, we analyze the characteristics of Seismic Disaster of Grottoes and discuss the calculation methods of four reinforcement conditions respectively. Meanwhile, though the discussing probe into seismic stability of the reinforcement.(2) For consolidation of the grottoes'slope, there's no mature theory and technique.In this paper the back analysis of shear strength of the rock slope at Yulin Grottoes is presented.Through the back analysis of shear strength,we can presents a procedure for the design of consolidation of the Yulin Grottoes in Anxi.It is very important in the field of reinforcing the slope of grottoes.(3) Based on the software of ADINA, author developed a program of prestress anchor cable. The steady of Grottoes attacked by earthquake is analyzed with the engineering soft named ADINA, in order to show where the weak parts of Grottoes are and Time-history curves of the horizontal displacement of the easily damaged nodes and Time-history curves of first and third principal stress of the easily damaged elements. Based on the assessment of seismic risk of surrounding rocks, three sections are selected to perform FEM calculating using ground acceleration history of different engineering properties as input. Through study of the displacement and stress fields of grotto surrounding rocks under ground motion of different PGA, frequency spectrum and duration, the influence of structure of grottoes and neighboring grottoes on dynamic damage and stability of country rock is discussed. The results show that the weak parts of Grottoes often are nearby at the corners of Grottoes and that to employ the anchoring steel-bars in the gaps does good to the safety of the whole structure of Grottoes.This research is financially supported by social welfare study No. 2002DIB20062 of Ministry of Science and Technology of China.